Include line-mixing for any CO2 lines for which pretabulated data exists.
Calculated ranges may be expanded to include entire affected bands
Ignore line mixing
Line-mixing is primarily a correction affecting spectral regions where
CO2 line-intensities, and densities, are greatest. However, it does add
significantly to the computational cost. The general recommendation is to
try running the RFM with/without the MIX flag for the required calculations
and see if it makes sufficient difference to justify its inclusion.
The line-mixing is a first order model from Tobin & Strow (1994),
See subroutine ymix_fnc.f90 for details.